Thermostatically-controlled switch



Dec. 6, 1927. A 1,652,143` Y G. W. HART v THERMOS TATI CALLY CONTROLLED SWI TCH Filed Nov. 16. 1925 p.

Patented Dec., 6, 1927.

UNllEJ@ STATES PATENT @FFI/CE.

GERALD W. HART, F WEST HARTFORD, CONNECTICUT, ASSIGNOR T0 THE HART MAN- UFACTURNG COMPANY, GF HARTFORD, CONNECTICUT, A CORPORATION 0F NEW JERSEY.

THER-MOSTATICALLYrCONTROLLED SWITCH.

Application led November 16, 1923. Serial No. 675,092.

rThis invention relates to circuit controlling apparatus' and includes various features of novelty and advantage which find peculiar adaptation in an apparatus for controlling, by means of a temperature responsive device, the heat of an electric heater or oven. The aim ot the invention is to provide an apparatus of this sort which is characterized by its extreme simplicity in construction, itsv conipactness in arrangement, neatness in appearance, its eiiiciency in operation, the ease and facility with which it may be adjusted and set to operate at any predetermined desired temperature, and by its strength and durability.

As will be seen from the following detailed description, my improved apparatus coniprises but a relatively few number of parts, each Ot which is ot simple construction, and these'parts are so arranged that injury thereto cannot result due to excessive temperatures. The device may be very uickly set so as to operate with accuracy an sensitiveness.

The above and other objects oit the invention are obtained in the structure shown in the accompanying drawings wherein is illustrated one of the embodiments which the present invention may take. lin these drawings:

Figure 1 is a view in side elevation of my improved apparatus; l

Fig. 2 is a central longitudinal section therethrough;

Fig. 3 is a plan view with-the cover removed; and

Fig. d is a detailed view, being taken on line 1 4 of Fig. 2.

liteterring to the drawings in detail, my improved apparatus includes an electric switch having a pair of stationary terminals or contacts and 11 and a switch arm 12 positioned therebetween; a thermostatic device comprising, in the present instance, a metal tube 13 and a carbon rod 14 therein; and a connection through which the thermostatic device moves the switch arm, this connection here being shown in thejorm ot a plungerl;

The switch elements are mounted on a plate of insulating material located within a base 21 of any suitable construction. The stationary contacts 10 and 11 are re.

epectively carriedl for adjustment by the strip 22 and the bracket 23 secured tothe insulating plate 20. The switch arm 12 is pivoted 1n the up-turned end ot the bracket 19.l ln

the present instance, this bracket has anv opening 24: and the end of the switch arm is notched, as at 25, so that the switch arm mayA The free end be hooked into the opening. ot' the arm carries a circuit closing member or pin 26 which "is suitably insulated from the arm. |llhe circuit closing member 26 is normally urged in the 'direction of the upper contact 11 by a spring 27 which also serves as a conducting member. One end of the spring isconnected to and in contact with the pin 26, and the other end ot the arm has sliding engagement in the groove 28 ot a contact strip or plate 29. rlhe arrangement of the spring 27 is of advantage in that the two functions or1 urging the switch arm upwardly and connecting 'the pin 26 to a source of current are obtalned in a very simple manner. Owing to the engagement of the spring in the groove 28, disarrangement of the spring is obviated. lt will be seen, particularly from Fig. 2, that the arm is carried about the plunger 15. Cooperating with the arm 12 adjacent its pivotal point is the free end of a relatively shorter lever 30 which is pivoted as at 31 in a bracket 19 through which the plunger slides. This lever extends through an elongated slot 33 in the plunger, there being such clearance between the lower side of the lever and the lower end ot this slot that there Yis never any engagement therebetween so that injury, which might otherwise result from the thermostatic device raising the plunger to entreme position, is guarded against.

rlhe tube 13 of the thermostatic device is preferably of a material having a high coefiicient of expansion while the rod 14 ytherein is of a material of relatively low coeliicient ot expansion, for instance carbon.`

one element of temperature is here shown as being in the form of a screw 40 screwed directlyinto a recess 1n the upper end of the plunger. The lowerl end of this screw is adapted to protrude into the slot 33 and engage the upper edge of the lever somewhat adjacent its pivotal po1nt 31. The screw is preliminarily adjusted within the plunger to determine the range of temperature within which the thermostat1c device will actuate the switch. In order to set or regulate this screw so that the thermostatic device will actuate the switch at any desired predetermined temperature within the selected range, the screw is connected to a rotatable cover 41 which carries indicating means. This element, in the present instance, takesthe form of a scale 42 cooperating with an indicating mark 43 on the base. This cover, it will be see n, in addition to serving as a means for setting the device to operate at any desired temperature, houses the switch mechanism. The cover may be adjustably connected 'to the screw in any suitable manner but, by preference, vthe cover is provided with a rotatably adjustable lug 44 adapted to engage in the'kerf of the screw 40. This lug is secured to a plate 45 journalled in the top `of the cover and is rotatably held at the top and bottom by plates 46 and 47 and screws 48. The plate 45 isslightly thinner than the cover so that the clamping plates 46 and 47 will engage the cover, thereby clamping the lug 44 1n adjusted position. The cover is provided with circumferential slots 49 in which en- -gage the ends ofscrews 50 so. that the cover may be rotated through a given arc, but cannot be accidentally displaced.

The operation of the device is brieflyf as follows. The stationary contacts 10 and `11 may `be electrically connected to a solenoid operated switch which controls the heating element of a range, for instance, in such manner that when the circuit closing member 26 is brought into engagement with the contact 11, the solenoid operated switch is operated to throw the current onto the heating element of the range, and `the current, through the contact 11, is broken, and when the switch arm is thrown into engagement with the lower contact 10, the remote switch is againI operated to throw the heat oii' of the oven, and the circuit is broken through the contact 10. This application of the switch is stated by way of illustration only. Assuming that i the range of temperature within which it is desiredv to maintain the heat-of the oven has been selected, the thermostatic device is heated-up as by placing it 'within a chamber, the temperature of which can be accurately controlled, or within the oven itself, to a predetermined temperature within the selectedl range. The cover 41 will be removed and the screw 40 will be so it. In this case, the plunger will be adjusted that `when the predetermined temperature has been reached the screw will engage the lever 30 and throw the switch closing element 26 down into engagement with the contact 10, and when the chamber cools below that temperature, the thermostatic device will raise the screw out of engagement with the lever 31 permitting the spring 27 tothrow the switch arm upwardly thereby bringing the circuit closing member 26 l so that the scale 42 will indicate that temperature at which the device is to be set, and then turning the lug 44 while it is within the kerf 40 so as to adjust the screw to a position where the thermostatic device will operate at the selected temperature.

Assuming that the device has been adjusted, as just described, so that the eective range of temperature is between 400 and 600 degrees, and that the pointer has been set, say on the mark indicating 450 degrees, it will be seen that when the oven, for instance, to which the device is applied, reaches 450 degrees, the tube 13 will have been elongated to such an extent that the plunger is lowered to a point where the lower end of the screw 40 engages and .depresses the lever' 30 and the switch arm 12,. bringing the circuit closing member 26 into engagement with the lower contact 10. The current on the heating element of the ovenwill now be thrown off. Should the oven continue to heat up after the switch arm has thus been thrown, no damage can result to the switch parts for the thermostatic device will leave the plunger 15 without exerting any pull on suspended on the level 14, and the only downward force exerted will be the compression of the spring 36 which is not suiliciently stron@ to jam the parts. After the ,oven cools o the tube 13 will contract, thereby raising the carbon rod 14, and when a temperature of approximately 450 degrees is reached, the plunger will be raised to move the screw out of engagement with the lever 30, and then the switch arm, under the influence of the spring 27, will be thrown intoengagement with the contact 11 and the controlling mechanismwith which the switch is associated will throw the current onto the heating element. 'Should the temperature vof the oven fall below 450 degrees, in which event the tube 13 would be further foreshortened, no injury or jamming of the switch parts would result owing to the fact that there is sufficient clearance between the lever 30 and the lower en'd of the slot 33. have lound, in actual practice, that the temperature of the oven may be controlled within very small limits.

it will 'be seen from the foregoing description, taken in connection with the illustrations of the accompanying drawing, that my improved apparatus is very simple in construction and effective in operation. The adjustment and setting oi the device may be very conveniently made. Owing to the a1- rangement of the lever 30 and the switch arm l2, movement ot the plunger is compounded, so that for a very slight movement of the plunger there is edected a larger movement of the Contact end of the switch arm, which means that the switch may be controlled with greater nicety. Preferably, there will be provided on each of the opposite sides of the cover di a scale such as shown at 42. Associated with each scale will be an indicatinglmark carried by the base. ln the present instance, the indicating .mark on one side is designated by the numeral 43, as heretofore described, and that on the other side by the numeral 43 (see Fig. The purpose of providing these two scales or temperature indicating means is to adapt the arrangement for both right hand and lett hand ranges.

l claim as my invention:

1. ln an apparatus ot the character described, a base, a thermostat to one side of said base, an electric switch mounted on the other side of said base, a connection actuated by said thermostat to control said switch, a cup-like cover rotatably mounted on said base and housing said switch, and means cooperative with said cover to adjust the effective length of said connection, said cover being provided with graduations cooperatingv with said base to indicate the adjustment of said connection.

2. In an apparatus of the character described, a base, a thermostat, anelectric switch, a plunger constituting a connection between said thermostat and said electric switch, a screw carried by said plunger to vary the edective length thereof, a cover rotatably mounted on said base, means for adjustably connecting said cover to said screw, and means for indicating the adjustment of said screw including a scale and an indicating mark, one of which is carried by said cover.

3. ln an apparatus of the character described, a base, a thermostat, an electric switch, a plunger constituting a connection between saidy thermostat and said electric switclna screw carried by said plunger to vary the eiiective length thereof, a cover rotatably mounted on said base, a lug adjustably carried by said cover and adapted' to engage in the korf of said screw, and

means. for clamping said lug to said cover in adjusted position.

4. ln an apparatus of the character described, a base, a thermostat, an electric switch, a plunger constituting a connection between said thermostat and said electric switch, a screw carried by said plunger to varxT the edective length thereof, a cover rotatably mounted on said base, means for adjustably connecting said cover to said screw, means for indicating the adjustment of-said screw including a scale and an indieating mark, one of which is carried by said cover, and means for limiting the extent of rotation ot said cover.

5. ln an apparatus ot the character described, a base, a temperature change responsive device located to one side ot said base, an electric switch mounted on the other side of: said base and including a pivoted arm, a.` connection between said thermostat and arm extending through said base and including an adjustable member i'or varying the e'ective length ot' said connection and engaging said arm to that side opposite to that of said device, ar cover rotatably mounted on said base and housing said switch and adjustably connected to said vmember, and means carried in part by said cover for indicating the setting ot said connection.

6. ln an apparatus of the character olescribed, a base, a thermostat, van electric switch mounted on said base, a connection between said thermostat and said switch and including an adjustable member for varying the edective length of said connection to determine the range ot operation, a cover rotatably mounted on said base and housing said switch and adjustably connected to said member to adjust the same to any desired temperature within the selected range, said cover being provided with graduatlons cooperating with said base to indicate the adjustment of said connection.

7. lln an apparatus of the character described, a base, an electric switch thereon having a pair of slightly spaced apart contacts, a pivoted switch arm having at its freev end a circuit closing member adapted to engage said contacts, a relatively short lever pivoted to saidbase and having its tree end in engagement with said arm adjacent the ulcrum of the latter, a spring normally urging said arm in a direction towards one of said contacts, a thermostatie device, and a plunger between said lever. and device arranged to throw said switch into engagement with the other ot said contacts, said plunger having an elongated slot through which said lever extends.

8. ln an apparatus of the character described, a base,- an electric switch thereon having a pair of slightly spaced apart contacts, a pivoted switch arm having at its loo lili) ,to engage said contacts, a relatively short lever pivoted to said base and having its free end in engagement with said arm adjacent thevfulcrlim of the latter, a spring -normally urging said arm in a direction towards one of said contacts, a thermostatic member adapted to engage said lever.

9. In anapparatus of the character described, a base, an electric' switch thereon having a pair of slightly spaced apart contacts, a switch arm pivoted at one end.and having' a circuit closing member at its free end vadapted to engage said contacts, a lever relatively shorter than said switch arm and adapted to engage the latter between its ends, a thermostatic device, and an operative connection between said device and lever, comprising a plunger engaging at one end against saiddevice and havin at its other end an adjustable screw engaging said lever, and a cover adjustably associated with said screw and bearing, at least in part, temperature indicating means.

yl0. In an apparatus of the character described, a base, an electric switch thereon having a pair of contacts, a pivoted arm having at itat-free end an insulated circuit closing member positioned between said contacts, a terI'xrina-l plate having a groove and a current carrying; 's ring having one end slidablyengagingzih the groove of said plate vandY electrically-connected at`its other end contacts and a switch arm, a connection actuatedby .said thermostat to control said switch and extending through said base, a cover for said switch and rotatably mounted, a screw for adjusting the relation between said thermostat and switch so that the thermostat will operate the switch at a selected temperature, said screw being connected to said cover and angularly adjustable therewith, and means carried in part by said cover for indicating the angular position of adjustment thereof and the position ofvadj ustment of said screw.

GERALD W. HART. 

